DJI Assistant 2 isn't reacting to me plugging in the controller.  The app doesn't say I need an update, but it would be nice to be able to confirm that it is up to date.  Is there a way?  I just updated my Spark, 2 batteries and the app and I want to make sure I'm all done.

Try connecting the RC to DJI GO app via Wifi.. it will check for the latest firmware before you tap "Go Fly". it might show you a warning in red color saying that the firmware is not up to date, then you can click that to proceed to update. but that might be a nasty work to switch between your RC wifi and your network. but gets the job done!!

You can check the current firmware as below: make sure the aircraft and controller have been powered on, then launch DJI GO 4, you will find it in General Settings>About.